Inhibitors of oxidative degradation

ABSTRACT

Novel secondary aromatic-aliphatic amines having anti-oxidant properties are prepared by reacting aromatic nitroso amines or phenols with olefins having at least one hydrogen atom attached to a carbon atom which is in the Alpha -position with respect to a carbon-carbon double bond. The reaction may be performed by heating the reactants together under an inert atmosphere in the presence of a polar or non-polar organic solvent, or using the olefin as a solvent.

0 mted States Patent 1151 3,689,513

Cain et al. 1 Sept. 5, 1972 [54] INHIBITORS OF OXIDATIVE OTHERPUBLICATIONS DEGRADATION Hamer et a1., Tetrahedron Letters No. 6, pages381 to [72] Inventors: Maurice Edward Cain, Welwyn 384 (1963).

Gard Cit B i Saving, w l Karrer, Organic Chemistry, 4th English Ed.,page 928, G ff Thomas Knight, sh ff -d Elsevier Publ. Co., New York1950. ll f E l Chemical Abstracts I, Vol. 52, Co]. 11182 (1958)(abstract of Endo). Assigneer The Natural fq Producers ChemicalAbstracts 11, V01. 56, C01. 5887 (1962) (ab- Research Association,London, stract of Ger. 1,104,522). England Misra et al., J. Ind. Chem.Soc. Vol. 37, pages 481- 22 F! d: u] 14 1969 482 (1960)- 1 J y Lattes etal., Comptes Rendus, V0]. 265, series 0, [21] Appl. No.: 841,610 pages341 to 344 (Aug. 1967).

Houben-Weyl, Methoden der Organischen Chemie, Band X/4, (4th Ed.), pages364 and 406- 407, Georg [30] Fore'gn Apphcanon Pnonty Data ThiemeVerlag, Stuttgart, Germany (March 1968).

July 23, 1968 Great Britain ..35,l94/68 Primary ExaminerJohn D. Randolph52 US. Cl. ..260/404.5, 252/401, 252/403, Attornekwendemfll, Lmd &Pollack 260/689, 260/800, 260/809 [57] ABSTRACT [51] Int. Cl. ..C07c87/50, C070 95/08 Novel secondary aromatic-aliphatic amines having [58]Field of Search ..260/240 G, 574, 577, 143 anti-oxidant properties areprepared by reacting aromatic nitroso amines or phenols with olefinshaving at [56] R f en e Cit d least one hydrogen atom attached to acarbon atom which is in the a-position with respect to a carbon-car-UNITED STATES PATENTS bon double bond. The reaction may be performed byheating the reactants together under an inert atgggi fg mosphere in thepresence of a polar or non-polar or- 1 v a 4 a u n n. f l 2,941,9216/1960 Darlington ..424/330 game Solvent or the ole m as a so vent3,445,531 5/1969 Anderson ..260/577 X 10 Claims, No Drawings INHIBITORSOF OXIDATIVE DEGRADATION This invention relates to inhibitors ofoxidative degradation, and in particular to certain novel secondaryaromatic-aliphatic amines, and to a process for their preparation.

The conventional preparation of I p-phenylenediamines involves thecatalytic hydrogenation of a mixture of a p-amine, p-nitro orp-nitroso-aniline and an aldehyde or ketone. A disadvantage of thishydrogenation reaction'is that it is only suitable for batch operation.A further disadvantage is that suitable ketones or aldehydes may beexpensive or not readily obtainable. By contrast, the thermal additionreaction of the present invention is capable, in principle, of beingoperated continuously. Also, it may be desirable to prepare antioxidantsof high molecular weights in order to minimize their removal from thesystem which they are protecting by volatilization, migration or solventaction; according to the present invention, paraphenylenediamine groupscan advantageously be introduced into large molecules by the use ofcheap and readily available unsaturated fats and oils.

The present invention provides a process for preparing a secondaryaromatic-aliphatic amine, which process comprises heating together a) anaromatic nitroso compound having the formula:

where R R R and R may be the same or different and each represent ahydrogen atom, a saturated or unsaturated aliphatic (includingalicyclic) group or an aryl, aralkyl or alkaryl group, which may containone or more non-carbon atoms, or may, in the case of formula (I) formone or more additional aromatic rings fused to the aromatic ring shownin the formula,

R R and R may be the same or different and each represent a hydrogenatom, a saturated or unsaturated aliphatic (including alicyclic) group,or an aryl, aralkyl or alkaryl group which may contain one or morenoncarbon atoms, or R and R together with the nitrogen atom to whichthey are attached form a heterocyclic ring which may contain one or moreother hetero atoms, and b) an olefin having at least one hydrogen atomattached to a carbon atom which is in the a-position with respect to thecarbon-carbon double bond, i.e., having the formula:

RRC CR-CHRR n where R in each case is a hydrogen atom or a saturated orunsaturated aliphatic (including alicyclic) group or an aryl, aralkyl oralkaryl group which may contain one or more other functional groups,provided that each group R contains not more than 100 carbon atoms.

It should be noted that large substituent groups, attached to thearomatic ring of the nitroso compound, may have the efiect of stericallyblocking either the nitroso group or the other functional group (e.g.amine or hydroxyl) so as to inhibit or prevent reaction. For example, ithas been found that di-tertiarybutyl nitrosophenol cannot easily bereacted in the manner set out above.

The invention also includes, as new compounds, the secondaryaromatic-aliphatic amines which can be prepared by the reaction definedabove, however prepared, i.e., when prepared by that reaction or by anyother reaction. Such compounds will have one of the two formulas below,in which R, R R R R R R and R have the significance set out above.

NH-C RRC 11:01:11

where R R R R R R and R have the same meaning as defined above.

Specific examples of preferred aromatic nitroso compounds are:

N,N-Dimethyl-p-nitrosoaniline DMNA N,N-Diethyl-p-nitrosoaniline DENAp-Nitrosodiphenylamine NDPA p-Nitrosophenol NP Other suitable aromaticnitroso compounds include 6- nitrosothymol; p-nitrosophenyl ethyl ether;2-methyl-4- nitrosophenol; 2,6-dimethyl-4-nitrosophenol; 2,6-diethyl-4-nitrosophenol; 2,6-diisopropyl-4- nitrosophenol;3-methyl-4-nitrosophenol; and 3,5- dimethyl-4-nitrosophenol.

The olefin to be used in the process of this invention may be determinedby economic considerations. Mention will be made of three preferredgroups of olefin. In one group comprising the commercially availableolefin hydrocarbons, the radicals R in the olefin RRC CR-CI-IRR arehydrogen atoms or saturated or unsaturated alkyl radicals containingfrom one to 20, particularly from one to six, carbon atoms. Specificexamples are 2- methylpent-Z-ene and 2-methyloct-2-ene. Another groupcomprises the naturally occurring unsaturated animal and vegetable fatsand oils, for example, pilchard oil, rapeseed oil, palm oil, castor oilor olive oil and unsaturated derivatives thereof, and the unsaturatedfatty acids, e. g. oleic acid, which may be obtained from them byhydrolysis. The third group comprises short-chain unsaturatedhydrocarbon polymers, containing about one double bond per molecule,such as are obtained during the Friedel-Crafts polymerization of simpleolefins, e.g., polybutene from isomeric butenes.

Any convenient olefin may be used according to the invention providedthat there is a hydrogen atom attached to the carbon atom which is inthe a-position to the carbon-carbon double bond. However, the rate ofreaction of a specific olefin depends on its detailed structure. Thus,tri-(alkyl substituted) ethylenes generally react faster than dior mono-(alkyl substituted) ethylenes.

The reaction of this invention is thought to take place via an 01-13shift of the double bond in the olefin molecule. The overall course ofthe reaction may be represented generally as:

where R, R", R', R" and R' are all within the above stated definition ofR, the nomenclature being used to illustrate the double bond shift.

The reaction between the aromatic nitroso compound and the olefin iseffected by heating the reactants together in the liquid phase. Theolefin may constitute the liquid medium; but the aromatic nitrosocompounds have only limited solubility in olefins, so a substantialexcess of the olefin may have to be used. A]- ternatively, a non-polarorganic solvent, such as, for ex ample, xylene or cyclohexane, may beused; such nonpolar solvents have little effect on the rate of reaction,compared to reaction performed in the absence of solvents, but mayslightly increase the yield.

In order to further increase the yield and reduce byproduct formation,compounds capable of acting as electron transfer reductants (forexample, 2 moles of zinc dimethyldithiocarbamate per mole of nitrosocompound) or as hydrogen atom donors (e.g. 1 mole of hydroquinone permole of nitroso compound) may be added as co-agents to the reactionmixture either in the presence or absence of a non-polar solvent. Caremust however be taken that the co-agent does not react with the aromaticnitroso compound. The effect of these coagents does not appear to be toincrease the rate of reaction, but to cut down the formation of otherproducts in side reactions, thus increasing the yield.

Alternatively, again, polar organic compounds, for example, dimethylsulphoxide, dimethyl formamide or isopropanol, may be used as solventsfor the reaction. These polar solvents decrease the rate of reaction butlead to a higher final yield by minimizing side reactions.

The temperature to which the reactants are heated is not critical.Reaction between DMNA and 2-methylpent-2-ene in the absence of solventwas found to be complete after 9 days at 35C.; at 100C. substantialreaction had occurred within 15 minutes and the reaction was complete in2% hours. However, yield decreases with increasing temperature, and itis therefore preferable to use as low a temperature as possibleconsistent with an adequate reaction rate, for example from 60 to C. inthe absence of polar solvents. When polar solvents are used, highertemperatures are generally desirable, e.g. from to 1 10C., in order tomake the reaction proceed fast enough, and higher temperatures of up toC. or more may be employed.

In air, the reaction is complicated by extensive sidereactions, and theyield of the desired secondary aromatic-aliphatic amine may be low. Itis therefore preferred to perform the reaction either under vacuum or aninert atmosphere, for example, nitrogen.

The formation of substituted p-phenylenediamines by the reaction ofN,N-dimethyl-p-nitrosoaniline, or N,N-diethyl-p-nitrosoaniline orp-nitrosodiphenylarnine with other olefins has been demonstrated byanalysis of the products by thin-layer chromatography on silica gel,mild oxidation of the plates converting the p-phenylenediamines to thecharacteristically colored Wurster radicals. The olefins giving positivereactions were 2-methylpent-2-ene, 2-methyloct-2-ene, squalene,pent-3-ene, 2-methyl-oct-1-ene, 4-methylpent-2-ene, l-methylcyclohex- 1-ene, 2,3-methylbut-2- ene, hex-I-ene and hex-2-ene, all of which fulfilthe requirements given for (III) above. Yields were estimated to be inthe range 40 to 70 percent based on the original nitroso compound.

Although it is apparently unnecessary in view of the high antioxidantactivity of the initial products, the unsaturated alkyl group in thesecondary amine produced may be hydrogenated according to the inventionto give the corresponding fully saturated compound.

The invention also envisages the use of these new secondary amines asinhibitors or retarders of oxidative degradation reactions such as occurin rubbers, fats, oils, cracked gasoline and petroleum.

The invention is illustrated by the following Examples.

(VIII) Et Et by heating 8.9 g. of N,N-diethyl-p-nitrosoaniline (DENA)with 16 g. of 2-methyl-pent-2-ene in xylene (25 mls.) under vacuum at140C. for 48 hours. Removal of the solvent gave 6g. of product, b.p.96/0.01 mm. (Found C, 78.0; H, 10.8 N, 11.5. C I-I N requires C, 78.1;H, 10.6; N, 11.3%). Its identity was confirmed as (VIII) by bothinfra-red and nuclear magnetic resonance spectroscopy.

EXAMPLE 2 N,N-Dimethyl-p nitrosoaniline (DMNA) (2.0 g.) and2-methyl-pent-2-ene mls.) were dissolved in dimethylformamide (80 mls.),the solution sealed in a glass ampoule under vacuum, and heated in anoil bath at 100C. for 16 hours. The solvent and excess of olefin wereremoved by distillation at water-pump pressure, and the residuedistilled under high vacuum. The dark red oil b.p. l20C./0.005 mm.weighed 1.32 g. (45 percent of theoretical yield), and was identified byits ultraviolet, infra-red, and nuclear magnetic resonance spectra andelemental analysis as N,N-dimethyl-N'-(lethyl-2-methylprop-2-enyl)-p-phenylenediamine (IX) as follows uv).,,,,,,=261.5 mu,log'e=4.19- L0.01

ir bands at 812 cm- (p-disubstituted benzene),- 895 cm (H C CR and 948cm- (CNC symmetrical stretch) nmr: peaks at 6.49 p CCHN, triplet,

splitting 6.5 cps) and 6.92 1- (NH), the integral of each correspondingto l proton nitrogen content 12.2 percent, C H N requires N,

12.8%. Gas-liquid chromatographic analysis of the product in comparisonwith p-phenylenediamines of known structures was also consistent withthe proposed structure (IX). The corresponding N,N- diethyl compound(VIII) was also prepared, in 45 percent yield, by the method of thisexample, using EXAMPLE3 N,N-Dimethyl-p-nitrosoaniline (DMNA) (5.0 g.),2- methyloct-2-ene (10 g.) and dimethylformamide (50 mls.) were heatedunder an atmosphere of nitrogen for 4 hours at l00-110C., when thinlayer chromatographic analysis of the mixture indicated completeconsumption of the nitroso compound. The solvent and excess of olefinwere distilled off at water-pump pressure, and the residue distilledunder high vacuum to give 3.5 g. (40 percent of theory) of a red oil,b.p. l10/0.001 mm. This was shown by analysis to be N,N-dimethyl- N'-(l-isopropenylhexyl) p-phenylendiamine (X) and had uv absorption A 262mp; loge 4.20 i 0.01, infrared absorption bands at 812 cm(p-disubstituted benzene), 893 cm". (l-l C CR and 948 cm (C N-Csymmetrical stretch) and proton nmr peaks at 6.42 1' C--CI-I--N,triplet, splitting 5.5 cps) and 6.857 (NH), the integral of eachcorresponding to one proton.

Found: N ll.5%.C, I-l N requires N, 10.8%. Gas liquid chromatographicretention times were consistent with the proposed structure.

EXAMPLE 4 p-Nitrosophenol (NP) (0.5 g.) and 2-methylpent-2- ene (6.8 g.)were dissolved in dimethylformamide (30 g.), sealed in vacuo and heatedat C. for an hour. Evaporation of the excess of olefin gave a semi-solidresidue which was extracted with chloroform, and the residue obtained onevaporation of the chloroform was then extracted with light petroleum(b.p. 3040C.). Preparative-scale thin layer chromatography yielded alight brown oil (0.05 g.) which was identified by ultra violet,infra-red and nuclear magnetic resonance spectroscopy as the expected1-hydroxy-4-(1-ethyl-2- methylprop-2-enylamino)-benzene (XI) as followsuv A 246 and 318 mu, the bathochromic shift of 10 my. compared withp-aminophenol (A 236 and 306 my.) being consistent with the secondaryamino structure ir bands at 820 cm (p-substituted benzene), 895 cm (Cl-ICR 3425 cm (CCL, sol"; RNH Ar) and 3610 cm (CCL, sol, ArOH) nmr peaks at6.37 CCHN and C- CI-I-O), 5.831- (NI-I and O-I-I) and 5.091- (CH theline integral of each corresponding to two EXAMPLE 5p-Nitroso-diphenylamine (NDPA) (10 g.), 2- methyloct-Z-ene (40 g.), zincdimethyl-dithiocarbamate (25 g.) and dimethylformamide (90 ml.s) wereheated for 5 hours at C. under nitrogen, after which time no NDPAremained unreacted. The product was treated with water, and the organiclayer separated off. The aqueous layer was removed from the solidprecipitate, and washed with light petroleum (b.p. 30-40C.). The organiclayer and petrol washings were combined and washed with 2N hydrochloricacid, the acid layer neutralized with dilute ammonia and the productextracted with petrol. The black residue obtained after evaporation ofthe petrol had ultraviolet and infra-red spectra consistent with theproposed structure (XII), the purity being assessed by thin-layerchromatography as 75 percent. The yield was 60 percent of theory.

The antioxidant properties of the -phenylenediamines VIII, IX, X and XIIwere evaluated in natural rubber vul- Natural rubber (Heveaerumb SMRSL)100 parts by weight Zinc oxide 5 Stearic acid 2N-Cyclohexylhenzothiazole-2- sulphenamide (CBS) 0.5 Sulphur 2.5 Curetime 40'/l40C.

The oxygen absorption of samples cut from l 10 0.3 cm. vulcanized sheetswas measured at 100C. The results are compared in Table l with thosegiven by three commercially available p-phenylenediamine antioxidants.

TABLE 1 Antioxidant activity of p-phenylenediamine (1 pphr) Commerciallyavailable as Nonex ZA Commercially available as Santoflex l3Commercially available as Santoflex 77 75% pure The Table shows that thenovel p-phenylenediamine antioxidants are equally as effective as thebest available saturated p-phenylenediamines.

The p-phenylenediamine (XII) prepared as described in Example wasevaluated for antiozonant activity in the gum vulcanizate formulationgiven above by testing in the ozone chamber at an ozone concentration ofpphm and a temperature of C. The results are given below.

Antiozonant activity of N-phenyl-N'-(iso-propenyl hexyl)-p-phenylenediamine Antiozonant Level Static Dynamic 0-2096 criticalstrain at 300 epm strain )6 hours to first crack None 7 4N-PhcnyI-N'-(isoprophenylhexyl)- p-phenylenediamine 4 20 30 The resultsshow a significant antiozonant activity for the novelp-phenylenediamine.

In Table 2 below, there are given various further examples which serveto show how the reaction conditions affect the yield. In all cases thetime of heating is that required to consume all the aromatic nitrosocompound. The yields of the p-phenylenediamines were measured bygas-liquid chromatographic analysis of the reaction products. Where asolvent is used, the concentration of the nitroso compound in thesolvent is 5 percent. Where no solvent is present, a 20-fold molarexcess of the olefin is used. Co-agents when used, are used at aconcentration of 2.3 moles per mole of nitroso compound.

TABLE2 Example Nitroso Olefin Solvent CoAgent Compound 6 DMNA MP NoneNone 7 DMNA MP None None 8 DMNA MP None None 9 NDPA MP None None 10 DMNAMP None ZDC l 1 NDPA MP None TBTU 12 DMNA MP None PPD 13 DMNA MPCyclohexane None 14 DMNA MP Xylene None 15 DMNA MP DMSO None 16 DMNA MPDMF None 17 DMNA MP Isopropanol None 18 DMNA MO DMF None 19 DMNA MO DMFNone Example Atmosphere Heating Yield Temp. Time of theory 6 Vacuum 35C.9 days 38 7 Vacuum 65C. 24 hours 36 8 Vacuum C. 2.5 hours 25 9 Vacuum100C. 2.5 hours 28 10 Vacuum 100C. 2.5 hours 40 ll Vacuum 100C. 2.5hours 43 12 Vacuum 100C. 2.5 hours 35 13 Vacuum 100C. 2.5 hours 32 14Vacuum 100C. 2.5 hours 34 15 Vacuum 100C. 16 hours 52 16 Vacuum 100C. 16hours 68 17 Vacuum 100C. 16 hours 57 18 Vacuum 100C. 16 hours 50 19Nitrogen 100C. 16 hours 40-50 MP is 2-methy1pent-2-ene MO is2-methyloct-2-ene DMSO is dimethyl sulphoxide DMF is dimethylformamideZDC is zinc dimethyldithiocarbamate TBTU is tributyl thiourea PPD is N-(l ,S-dimethylbutyl)-N'-phenyl'p-phenylencdiamine.

The following Examples relate to products obtained by reacting aromaticnitroso compounds with higher molecular weight olefins, particularlynaturally occurring fats and oils. By contrast with most conventionalantioxidants, these products have the virtue of not being readily oraccidentally removed from the media into which they have beenincorporated as protection against oxidative degradation. Articles ofthe medium concerned, for example, rubber hoses, hot-water bottles andmotor vehicle tipes, can be used in contact with water or other solventswith less risk of the antioxidant being leached out.

The most efficient antioxidants, the substituted pphenylenediamines,discolor badly during ageing and exposure to light and they are normallyused in darkcolored articles only. Migration of the antioxidant is1iable to cause staining of neighboring light-colored articles. Theantioxidants described in the following Examples have the advantage,owing to the comparatively large size of their molecules, of a muchreduced tendency to migration.

EXAMPLE 20 NDPA (2 g.) and a light polybutene oil obtained by thepolymerization of mixed butenes (average m.w. 260, 50 mls.) were heatedunder nitrogen at 100C. till all the NDPA had reacted (5 hours). Theproduct was distilled under high vacuum to give a dark red oil, b.p. ca200/0.002 mm, the uv spectrum being consistent with the formulation asN-phenyl-N'-(polybutenyl)-pphenylenediamine.

EXAMPLE 21 DENA (2 g.) and the polybutene used in the previous example(50 mls.) were similarly heated under nitrogen at 100C. to completereaction. A sample of the crude reaction product was tested forantioxidant activity. The bulk was treated with light petroleum (b.p.3040C.), and washed with water (3X50 mls.). The petroleum solution wasthen washed with 2N hydrochloric acid (3 X 100 mls.), some difficultybeing experienced due to the formation of an emulsion. The acid washingswere combined, neutralized by the addition of dilute ammonia solution,and the product extractcd with light petroleum (b.p. 30-40C., 3 X 75mls.). The residue obtained after evaporation of the petrol after dryinggave a dark oil whose ultraviolet spectrum was consistent with itsformulation as N,N- diethyl-N-(polybutenyl)-p-phenylenediamine.

EXAMPLE 22 NDPA (2 g.), palm oil g.) and dimethylforrnamide (50 mls.)were heated under nitrogen at 100C. until no NDPA was detectable bythin-layer chromatography. The solvent was distilled off at reducedpressure and the modified oil used without further purification.

EXAMPLE 23 Fish oil represents a cheap source of highly unsaturated oil.Refined pilchard oil (40 g.) was heated under nitrogen with NDPA (10 g.)or DENA (10 g.) at 100C. for 5 hours with stirring. The resultingadducts were used without further purification.

EXAMPLE 24 Amount added Minutes to Oil treated to squalene 1% 0,absorption No addition 6 Castor oil 6.3% 2280 Tung oil 4.3% 1140 Theantioxidant activity of the products described in Examples 20-24 wereevaluated in the NR gum vulcanizate given after Example 5 above bymeasurement of the oxygen absorption of the vulcanizates at C. beforeand after an extraction process consisting of immersing the sheet incold running tap water for seven days. The results are given in Table 3.

The first of these three compounds is almost as effective as Nonox ZAbefore extraction, and slightly superior to Santoflex B afterextraction. The perfonnance of the treated palm oil, which can onlycontain at the most 20 percent of p-phenylenediamine W species, isnoteworthy. Furthermore the gum vulcanizate containing theN-phenyl-N-poly-butenyl-p-phenylenediamine was much lighter in colorthan usual with this type of antioxidant, approaching that of a controlwith no antioxidant. The last five products listed were not tested afterwater extraction.

EXAMPLE 25 A repeat preparation of the modified palm oil was carried outby heating NDPA (20 g.), palm oil (50 g.) and hydroquinone at 100C.under nitrogen with stirring for 6 hours. The product gave a similarantioxidant activity in the gum vulcanizate to that of Example 22.

A black filled vulcanizate was prepared using the base compound: naturalrubber (ribbed smoked sheet 1), 100; Zn0, 5; stearic acid, 2; highabrasion furnace black, 45; processing aid (Dutrex R), 5; CBS, 0.5;sulphur, 2.5. Test pieces were cured 40'] The initial physicalproperties of a control vulcanizate and those prepared with 6 pphr ofthe crude product were very similar; 12 pphr of adduct giving somereduction in properties:

The vulcanizates were retested after air oven ageing at 100C. forvarious times, the retention of physical properties of the protectedvulcanizates being higher than that of the control.

Ageing of a black vulcanizate Retention of property 1 day/100C. 3days/100C.

Treated palm oil,pphr T.S. EB M T.S. EB M 5 0 6| 76 116 19 45 71 a 81 so129 26 42 11s 12 86 84 130 33 48 122 EXAMPLE26 A carboxylic acid isnecessary in the formulation of a rubber vulcanizate to act as anactivator of the curing system. Commercially stearic acid is normallyused. By reacting the unsaturated analogue, oleic acid, with a nitrosocompound it should be possible to produce a combinedactivator/antioxidant.

NDPA (10 g.) was heated with oleic acid (50 g.) in dimethylformamideunder nitrogen at 100C. for 5 hours. The solvent was distilled off undervacuum and the modified acid used as a cure activator and antioxidant inthe gum vulcanizate described above. Its activating properties werealmost identical to those shown by stearic acid, and some antioxidantactivity was also observed.

EXAMPLE 27 Facticc is a material used as an additive in certain rubbervulcanizates for the purpose of aiding processing and extrusioncharacteristics, and is prepared by stirring rapeseed oil with about 25parts per hundred of sulphur, equally together with an organicaccelerator at a temperature of 160C. until the mixture forms a gel.Refined rapeseed oil (100g), sulphur (25g), diethanolamine (5g) and NDPA(10g) were heated with stirring at 160C., when gelation occurred after65 minutes. A similar preparation without the NDPA gave a similargelation time, the method of preparation being taken from BritishSpecification No. 588,353.

Both factices were tested in the black filled vulcanizate whosecomposition is given in Example 25. Test pieces were cured at a curetime of 40 minutes at 140C.

Samples from 10 X 10 X 0.3 cm sheets were tested by measuring the oxygenabsorption at 100C. before and after extraction withmethanol/acetone/chloroform azeotrope or water.

Hours to 1% oxygen absorption water extracted 14 20 UnextractedAzeotrope extracted 2O 8 Factice NDPA-treated factice 5 5 where R R Rand R may be the same or different and each represents a hydrogen atomor a lower alkyl group, and R R and R, may be the same or different andeach represents a hydrogen atom or an alkyl group or phenyl group, andwith b. an olefinically unsaturated compound having at least onehydrogen atom attached to a carbon atom which is in the a-position tothe double bond, selected from the group consisting of i. a hydrocarbonof the formula RRC CR- CHRR, wherein R is hydrogen or a saturated orunsaturated hydrocarbon group containing from one to 20 carbon atoms;

ii. naturally occuring unsaturated animal and vegetable fats and oils orthe carboxylic acids obtained from them by hydrolysis;

iii. short-chain unsaturated hydrocarbon polymers containing about onedouble bond per molecule; the molar proportion of reactant (b) presentbeing at least about 2.5 times the molar proportion of reactant (a)present, said reaction being performed by heating the reactants togetherat a temperature of from 35 to C in the absence of an organic solvent orat a temperature of from 35 to C in the presence of an inert organicsolvent.

2. A process as claimed in claim 1, wherein the radicals R in the olefinare hydrogen atoms or saturated or unsaturated alkyl groups containingfrom one to six carbon atoms.

3. A process as claimed in claim 1, wherein the reactants are heatedtogether for a time between a quarter of an hour and 9 days under vacuumor an inert atmosphere.

4. A process as claimed in claim 1, wherein the reaction is performed byheating the reactants in the absence of a solvent at a temperature from60 to 100C.

5. A process according to claim 1 wherein the molar proportion ofreactant (b) is at least about 4 times the molar proportion of reactant(a).

6. A process according to claim 1 wherein the molar proportion ofreactant (b) is at least about 4 times the molar proportion of reactant(a).

7. A process as claimed in claim 2, wherein the olefinically unsaturatedcompound is 2-methylpent-2- ene or 2-methyloct-2-ene.

8. A process as claimed in claim 2, wherein the olefinically unsaturatedcompound is pilchard oil, rapeseed oil, palm oil, castor oil or thecarboxylic acids derived therefrom by hydrolysis.

9. A process as claimed in claim 8, wherein the olefinically unsaturatedcompound is oleic acid.

10. A process as claimed in claim 1, wherein the olefinicallyunsaturated compound is obtained by Friedel-Crafts polymerization ofbutene.

2. A process as claimed in claim 1, wherein the radicals R in the olefinare hydrogen atoms or saturated or unsaturated alkyl groups containingfrom one to six carbon atoms.
 3. A process as claimed in claim 1,wherein the reactants are heated together for a time between a quarterof an hour and 9 days under vacuum or an inert atmosphere.
 4. A processas claimed in claim 1, wherein the reaction is performed by heating thereactants in the absence of a solvent at a temperature from 60* to 100*C.
 5. A process according to claim 1 wherein the molar proportion ofreactant (b) is at least about 4 times the molar proportion of reactant(a).
 6. A process according to claim 1 wherein the molar proportion ofreactant (b) is at least about 4 times the molar proportion of reactant(a).
 7. A process as claimed in claim 2, wherein the olefinicallyunsaturated compound is 2-methylpent-2-ene or 2-methyloct-2-ene.
 8. Aprocess as claimed in claim 2, wherein the olefinically unsaturatedcompound is pilchard oil, rapeseed oil, palm oil, castor oil or thecarboxylic acids derived therefrom by hydrolysis.
 9. A process asclaimed in claim 8, wherein the olefinically unsaturated compound isoleic acid.
 10. A process as claimed in claim 1, wherein theolefinically unsaturated compound is obtained by Friedel-Craftspolymerization of butene.